Synthesis and characterization of CD133 targeted aptamer-drug conjugates for precision therapy of anaplastic thyroid cancer

Aptamers as an approach to targeted cancer therapy

Conventional cancer treatments can cause serious side effects because they are not specific to cancer cells and can damage healthy cells. Aptamers often are single-stranded oligonucleotides arranged in a unique architecture, allowing them to bind specifically to target sites. This feature makes them an ideal choice for targeted therapeutics. They are typically produced through the systematic evolution of ligands by exponential enrichment (SELEX) and undergo extensive pharmacological revision to modify their affinity, specificity, and therapeutic half-life. Aptamers can act as drugs themselves, directly inhibiting tumor cells. Alternatively, they can be used in targeted drug delivery systems to transport drugs directly to tumor cells, minimizing toxicity to healthy cells. In this review, we will discuss the latest and most advanced approaches to using aptamers for cancer treatment, particularly targeted therapy overcoming resistance to conventional therapies.

[Is it possible to detect surface antigen CD133 on patient-derived glioblastoma continuous cell cultures using fluorescent aptamers?]

Theranostics combines diagnostics and therapeutic exposure. Regarding glioblastomas, theranostics solves the problem of detecting and destroying tumor stem cells resistant to irradiation and chemotherapy and causing tumor recurrence. Transmembrane surface antigen CD133 is considered as a potential marker of tumor stem cells.

OBJECTIVE

To detect CD133 in patient-derived glioblastoma continuous cell cultures using fluorescence microscopy and modified aptamers (molecular recognition elements) anti-CD133.

MATERIAL AND METHODS

To detect CD133, we used mousey fluorescence monoclonal antibodies anti-CD133 MA1-219, FAM-modified DNA aptamers anti-CD133 AP-1-M and Cs5. Non-aptamer DNA oligonucleotide NADO was used as a negative control. Detection was performed for three samples of patient-derived glioblastoma continuous cell cultures coded as 1548, 1721 and 1793.

RESULTS

MA1-219 antibodies brightly stained cell culture 1548, to a lesser extent - 1721. There was diffuse staining of cell culture 1793. Cs5-FAM aptamer stained cells in a similar way, but much weaker. AP-1-M-FAM aptamer interacted with cells even weaker and diffusely stained only cell culture 1793. Non-aptamer NADO did not stain cell culture 1548 and very weakly diffusely stained cell culture 1793.

CONCLUSION

For both molecular recognition elements (MA1-219 antibody and Cs5 aptamer), 3 cell culture samples can be arranged in the following order possibly reflecting CD133 status decrease: strong signal for cell culture 1548, much weaker for 1721, even weaker for 1793. Only cell culture 1548 can be considered CD133 positive with combination of Cs5+ and NADO signals. Cell culture 1793 is CD133 false positive with combination of Cs5+ and NADO+ signals.

Current Application of Nanoparticle Drug Delivery Systems to the Treatment of Anaplastic Thyroid Carcinomas

Anaplastic thyroid carcinomas (ATCs) are a rare subtype of thyroid cancers with a low incidence but extremely high invasiveness and fatality. The treatment of ATCs is very challenging, and currently, a comprehensive individualized therapeutic strategy involving surgery, radiotherapy (RT), chemotherapy, BRAF/MEK inhibitors (BRAFi/MEKi) and immunotherapy is preferred. For ATC patients in stage IVA/IVB, a surgery-based comprehensive strategy may provide survival benefits. Unfortunately, ATC patients in IVC stage barely get benefits from the current treatment. Recently, nanoparticle delivery of siRNAs, targeted drugs, cytotoxic drugs, photosensitizers and other agents is considered as a promising anti-cancer treatment. Nanoparticle drug delivery systems have been mainly explored in the treatment of differentiated thyroid cancer (DTC). With the rapid development of drug delivery techniques and nanomaterials, using hybrid nanoparticles as the drug carrier to deliver siRNAs, targeted drugs, immune drugs, chemotherapy drugs and phototherapy drugs to ATC patients have become a hot research field. This review aims to describe latest findings of nanoparticle drug delivery systems in the treatment of ATCs, thus providing references for the further analyses.

DNA-Based Nanomaterials as Drug Delivery Platforms for Increasing the Effect of Drugs in Tumors

DNA nanotechnology has significantly advanced and might be used in biomedical applications, drug delivery, and cancer treatment during the past few decades. DNA nanomaterials are widely used in biomedical research involving biosensing, bioimaging, and drug delivery since they are remarkably addressable and biocompatible. Gradually, modified nucleic acids have begun to be employed to construct multifunctional DNA nanostructures with a variety of architectural designs. Aptamers are single-stranded nucleic acids (both DNAs and RNAs) capable of self-pairing to acquire secondary structure and of specifically binding with the target. Diagnosis and tumor therapy are prospective fields in which aptamers can be applied. Many DNA nanomaterials with three-dimensional structures have been studied as drug delivery systems for different anticancer medications or gene therapy agents. Different chemical alterations can be employed to construct a wide range of modified DNA nanostructures. Chemically altered DNA-based nanomaterials are useful for drug delivery because of their improved stability and inclusion of functional groups. In this work, the most common oligonucleotide nanomaterials were reviewed as modern drug delivery systems in tumor cells.

Advances in aptamer-mediated targeted delivery system for cancer treatment

Aptamers with high affinity and specificity for certain targets have rapidly become a novel class of targeted ligands applicated in drug delivery. Based on the excellent characteristics of aptamers, different aptamer-mediated drug delivery systems have been developed, including aptamer-drug conjugate (ApDC), aptamer-siRNA, and aptamer-functionalized nanoparticle systems for the effective treatment of cancer, which can reduce potential toxicity and improve therapeutic efficacy. In this review, we summarize the recent progress of aptamer-mediated delivery systems in cancer therapy, and discuss the application prospects and existing problems of innovative approaches based on aptamer therapy. Overall, this review aims to better understand the current aptamer-based targeted delivery applications through in-depth analysis to improve efficacy and develop new therapeutic methods which can ultimately improve treatment outcomes for cancer patients.

Recent advances in aptamer-based therapeutic strategies for targeting cancer stem cells

Cancer stem cells (CSCs) are believed to be the main cause of chemotherapy resistance and tumor relapse. Various therapeutic strategies to eliminate CSCs have been developed recently. Aptamers, also called "chemical antibodies", can specifically bind with their molecular targets through special tertiary structures. The advantages of aptamers, such as lower immunogenicity and smaller size, make them superior to conventional antibodies. Therefore, aptamers have been used widely as targeting ligands for CSC-targeted therapeutic strategies in different tumor types. To date, various therapeutic cargoes have been conjugated to aptamers to kill CSCs, such as chemotherapy drugs, small interfering RNAs, and microRNAs. Aptamer-based targeted therapies for CSCs have made great progress in recent years, especially the development of multifunctional aptamer-based therapeutic strategies. Besides, cell-systematic evolution of ligands by exponential enrichment has been applied to screen new aptamers that might have a higher binding ability for CSCs. In this review, we focus on recent advances and introduce some new modalities of aptamer-drug conjugates against CSCs. Some considerations of the advantages and limitations of different aptamer-based targeted therapies for CSCs are also discussed.

The Landscape of Nucleic-Acid-Based Aptamers for Treatment of Hematologic Malignancies: Challenges and Future Directions

Hematologic malignancies, including leukemia, lymphoma, myeloproliferative disorder and plasma cell neoplasia, are genetically heterogeneous and characterized by an uncontrolled proliferation of their corresponding cell lineages in the bone marrow, peripheral blood, tissues or plasma. Although there are many types of therapeutic drugs (e.g., TKIs, chemotherapy drugs) available for treatment of different malignancies, the relapse, drug resistance and severe side effects due to the lack of selectivity seriously limit their clinical application. Currently, although antibody-drug conjugates have been well established as able to target and deliver highly potent chemotherapy agents into cancer cells for the reduction of damage to healthy cells and have achieved success in leukemia treatment, they still also have shortcomings such as high cost, high immunogenicity and low stability. Aptamers are ssDNA or RNA oligonucleotides that can also precisely deliver therapeutic agents into cancer cells through specifically recognizing the membrane protein on cancer cells, which is similar to the capabilities of monoclonal antibodies. Aptamers exhibit higher binding affinity, lower immunogenicity and higher thermal stability than antibodies. Therefore, in this review we comprehensively describe recent advances in the development of aptamer-drug conjugates (ApDCs) with cytotoxic payload through chemical linkers or direct incorporation, as well as further introduce the latest promising aptamers-based therapeutic strategies such as aptamer-T cell therapy and aptamer-PROTAC, clarifying their bright application, development direction and challenges in the treatment of hematologic malignancies.

Aptamers: an emerging navigation tool of therapeutic agents for targeted cancer therapy

Chemotherapeutic agents have been used for the treatment of numerous cancers, but due to poor selectivity and severe systemic side effects, their clinical application is limited. Single-stranded DNA (ssDNA) or RNA aptamers could conjugate with highly toxic chemotherapy drugs, toxins, therapeutic RNAs or other molecules as novel aptamer-drug conjugates (ApDCs), which are capable of significantly improving the therapeutic efficacy and reducing the systemic toxicity of drugs and have great potential in clinics for targeted cancer therapy. In this review, we have comprehensively discussed and summarized the current advances in the screening approaches of aptamers for specific cancer biomarker targeting and development of the aptamer-drug conjugate strategy for targeted drug delivery. Moreover, considering the huge progress in artificial intelligence (AI) for protein and RNA structure predictions, automatic design of aptamers using deep/machine learning techniques could be a powerful approach for rapid and precise construction of biopharmaceutics (i.e., ApDCs) for application in cancer targeted therapy.

A GD2-aptamer-mediated, self-assembling nanomedicine for targeted multiple treatments in neuroblastoma theranostics

Because current mainstream anti-glycolipid GD2 therapeutics for neuroblastoma (NB) have limitations, such as severe adverse effects, improved therapeutics are needed. In this study, we developed a GD2 aptamer (DB99) and constructed a GD2-aptamer-mediated multifunctional nanomedicine (ANM) with effective, precise, and biocompatible properties, which functioned both as chemotherapy and as gene therapy for NB. DB99 can bind to GD2⁺ NB tumor cells but has minimal cross-reactivity to GD2⁻ cells. Furthermore, ANM is formulated by self-assembly of synthetic aptamers DB99 and NB-specific MYCN small interfering RNA (siRNA), followed by self-loading of the chemotherapeutic agent doxorubicin (Dox). ANM is capable of specifically recognizing, binding, and internalizing GD2⁺, but not GD2⁻, NB tumor cells in vitro. Intracellular delivery of ANM activates Dox release for chemotherapy and MYCN-siRNA-induced MYCN silencing. ANM specifically targets, and selectively accumulates in, the GD2⁺ tumor site in vivo and further induces growth inhibition of GD2⁺ tumors in vivo; in addition, ANM generates fewer or no side effects in healthy tissues, resulting in markedly longer survival with fewer adverse effects. These results suggest that the GD2-aptamer-mediated, targeted drug delivery system may have potential applications for precise treatment of NB.

Next-Generation Molecular Imaging of Thyroid Cancer

An essential aspect of thyroid cancer (TC) management is personalized and precision medicine. Functional imaging of TC with radioiodine and [18F]FDG has been frequently used in disease evaluation for several decades now. Recently, advances in molecular imaging have led to the development of novel tracers based on aptamer, peptide, antibody, nanobody, antibody fragment, and nanoparticle platforms. The emerging targets-including HER2, CD54, SHP2, CD33, and more-are promising targets for clinical translation soon. The significance of these tracers may be realized by outlining the way they support the management of TC. The provided examples focus on where preclinical investigations can be translated. Furthermore, advances in the molecular imaging of TC may inspire the development of novel therapeutic or theranostic tracers. In this review, we summarize TC-targeting probes which include transporter-based and immuno-based imaging moieties. We summarize the most recent evidence in this field and outline how these emerging strategies may potentially optimize clinical practice.